System for electrical transmission and reception of pictures, documents, and the like



March 20, 1934. v. YANOUCHEWSKY ,7

SYSTEM FOR ELECTRICAL TRANSMISSION AND RECEPTION OF PICTURES, DOCUMENTS,AND THE LIKE Filed March 20, 1932.

Human //vz//v70/e VlAD/N/R m/voucuswszrr 14 TTORNEYS Patented Mar. 20,1934 SYSTEM FOR ELECTRICAL TRANSMISSION AND RECEPTION F PICTURES, DOCU-MENTS, AND THE LIKE Vladimir Yanouchewsky, Le Chesnay, France, as-

signor to Etablissements Edouard Belin, Paris,

France, a corporation Application March 20,

of France 1931, Serial No. 524,094

In France March 29, 1930 4 Claims.

My invention relates to devices for identically reproducing a phenomenonA, through intermediary steps B, C, D, etc.

For instance, if A is a luminous point of a vari- 5 able intensity,which is to be identically reproduced at a certain distance, thevariations of intensity of this point will be photoelectricallytransformed into variations of current, which may be called step B.These variations of current will be transmitted to a receiver, whichconstitutes step C. Finally, at the receiving station, a phenomenonpermitting to transform varia tions of current into luminous variations(step D) will make it possible, under certain conditions, to identicallyreproduce the original phenomenon A. Obviously, in most cases, the lawof variation of intermediate state B as a function of correspondingvariations of phenomenon A, the law of variation of intermediate state Cas a function of 0 B, and so on, in short the law of variation of theeffect with respect to the law of variation of the cause that determinessaid effect, will not be a linear law.

Be that as it may, if certain laws from cause to effect are not linear(From A to B, from B to C, for instance) and introduce into thesuccessive steps of the reproduction what may be termed a deformation,it Will be necessary that other laws from cause to effect (from C to Dand from D to A, for example) should introduce an inverse deformation,if the original phenomenon is to be reproduced.

The object of my invention is to provide means through which certain ofthese laws can be acted upon in order to compensate for the deformationsintroduced by other ones.

Although the arrangement that will be hereinafter described could beapplied to various possible uses of the detected currents, itsapplication to phototelegraphy will be particularly described, merely byway of example.

In the system for transmitting half-tone pictures, making use ofreflected light for exploring the picture, the photoelectric currentsthat correspond to the black portions of the document are exceedinglyfeeble and the differences between such currents for very dark portionsare very small. On the contrary, the differences are very importantbetween currents corresponding to light shades. In other words, thevariation of the photoelectric current as a function of half tints isvery different from a linear function. At the receiving station it isvery important to so modify the laws of detection that, account beingtaken of the curves of blackening of the photographic emulsions'that areused, the shades of the original may be accurately reproduced by meansof an apparatus transforming electric variations into luminousvariations.

For this purpose I amplify the incoming current from the emittingphotoelectric amplifier by means of two or more circuits havingdifferent characteristics and I provide means for subsequently detectingsaid current in different manners in each of these circuits.

A particular embodiment of my device will be hereinafter described withreference to the appended drawing, given merely by way of example, andin which Fig. 1 is a diagrammatic view of an electric arrangementadapted to be used in connection with the above mentioned application.

Figs. 2 and 3 are diagrammatic representations of the operation of thetubes by reference to the characteristic curves of the same.

The incoming current is sent into transformer T, then amplified anddetected by two separate circuits.

The first one includes T1, T1, T1", and R and will be called circuit 1.

The second one includes T2, T2, T2, and will be called circuit 2.

The two circuits are connected together in Z and in the common circuit(or in another one coupled therewith) is located apparatus E, whichserves to transform electric variations into luminous variations. Thecircuits located before the detecting tubes of each circuit 1 and 2 arearranged in such manner that the alternating amplitude applied to thedetectors of circuit 1 may be adjustable and higher than that applied tothe detectors of circuit 2.

That difference of amplitude may be obtained for example, by usingeither an input transformer having several different terminals on itssecondary (see the figure) or amplifying tubes having differentcharacteristic or still a supplementary stage of amplification on one ofthe branches and so on.

The detector or detectors (T1', T1") of circuit 1 on the grids of whichis applied a great alternating amplitude are but little polarized. Thelow value of this polarization makes it possible by operating in thehigher portion of the charicteristic, to block the amplifier when thealternating amplitude exceeds a certain value.

The detectors of circuit 2 are normally polar- 1266. and the alternatingamplitude applied to their grids is smaller than in circuit 1.

Detection accordingly takes place along the straight parts of thecharacteristics.

Finally a resistance R having suitable value inserted in the platecircuit of the detectors of circuit 1 makes it possible to regulate therelative action of the two detections of circuit 1 and 2 respectively.Through adjustment of the amplitude at the input terminals of therectifying tubes of each of the circuits, of the polarization and of thevalue of R, it is possible to choose the points of the characteristicsof the lamps about which said lamps are caused to Work in such mannerthat the curve of current intensities as a function of the shades mayWithin certain limits, be modified at will.

As above stated, the example shown is but a particular type ofapplication. This method of modifying the law of detection may beadapted to any other kinds of application for obtaining the best resultfrom the effects received at the input end in order to have them produceat the output end an sheet which is correct with respect to the cause ofthe effects received at the input end.

What I claim is:

1. In electric systems for identically reproducing a given phenomenonwhich include for transforming the variations of this phenomenon intovariations of an electric current, an arrangement comprising anapparatus for transform" ing variations of an electic current back intovariations of the phenomenon to be reproduced two circuits connected inparallel to apparatus, an amplifying tube and a detecting tube in eachcircuit, the detecting tube of the first circuit being less polarizedthan that of the second circuit, means for feeding the electric currentwhose variations correspond to those of the original phenomenon to bereproduced to the grids of the above mentioned amplifying tubes, andmeans for causing the amplitude of the current fed to the amplifyingtube of the first circuit to be greater than that of the current fed tothe amplifying tube of the second circuit.

2. In electric systems for identically reproducing a given phenomenonwhich include means for transforming the variations of this phenomenoninto variations of an electric current, an arrangement comprising anapparatus for transforming variations of an electric current back intovariations of the phenomenon to be reproduced, two circuits connected inparallel to said apparatus, an amplifying tube and two detecting tubesin each circuit, the detecting tubes of the first circuit being lesspolarized than those of the second circuit, a transformer for feedingthe electric current whose variations correspond to those of theoriginal phenomenon to be reproduced to the grids of the above mentionedamplifying tubes, a plurality of terminals on the secondary of saidtransformer connected to the amplifying tubes of the two circuits insuch manner that the amplitude of the current fed to the first circuitis greater than that of "he current fed to the second circuit.

An arrangement accor to claim 1 further comprising a resistance insertedin the plate circuit of the detecting tube of one of the above namedcircuits for regulating the relative action of these two circuits on theapparatus for converting variations of the electric circuit intovariations of the phenomenon to be reproduced.

t. An arrangement according to claim 2 further characterized in theplates of the two detecting tubes of circuit are connected in parallelto the above named apparatus, and comprising a resistance inseredbetween the plates of the detecting tubes of one circuit and saidapparatus for regulating the combined action of the two circuits on saidapparatus.

VLADIMIR YANOUCHEW' SKY.

